Friendship, amity, comity, goodwill are comparable when they denote the relation (or, in the first three instances, the alliance) existing between persons, communities, states, or peoples that are in accord and in sympathy with each other.
Friendship is the strongest of these terms in its implications of sentiment in the relation and of closeness of attachment. Sometimes it suggests an alliance; at other times it excludes that suggestion.
Amity implies the absence of enmity or discord. Positively, it may imply nothing more than amicable relations or it may suggest reciprocal friendliness. Often the term suggests benevolent understanding and mutual tolerance of potentially antagonistic aims or views.
Comity has come to imply comradeship based either upon an interchange of courtesies or upon a similarity of interests and aims. The word often denotes a group bound together by friendship or by common interests but without implying loss of independence by members of the group or transference of sovereignty from the members to the group.
Goodwill derives its chief implication of a benevolent attitude or of reciprocal good feeling largely from the Authorized Version’s translation of the Angelic Hymn. The term is often used in international diplomacy to designate a reciprocal friendliness which constitutes an informal bond between nations and works to the advantage of all concerned.